UPDATE 5:10 PM, 7/20: Maybe some more storms where Thursday evening’s squall line came from
UPDATE 5:10 PM, 7/20: Clouds have kept temperatures down today across most of Southwest Virginia, and therefore, instability has been lacking, and there has been much less shower and thunderstorm development than projected. There is a line of showers/storms near the Ohio River about to cross into West Virginia that is rather slowly pushing southeastward and may affect our region later this evening, likely after sunset. There are also a few showers and storms developing ahead of that line. Similar to last night, we’ll keep an eye on this on radar through the evening. END UPDATE
UPDATE 8:45 AM, 7/20: The Storm Prediction Center has shifted the slight risk zone for severe storms to locations east of the Blue Ridge, where there will be greater heating and therefore atmospheric instability today. Further west, showers and storms are numerous north and west of the Roanoke Valley this morning (latest radar linked here), and additional storms are likely to redevelop later today as a cold front pushes into the host, sticky air mass in place. Expect splotchy coverage of rainfall — heavy for some, light for many, none for others — rather than areawide general rain. END UPDATE
We have a dozen windy cold fronts each winter – and then we had the Feb. 10, 2008, tree-toppling, wildfire-spreading, all-day windstorm. Similarly, we typically have maybe a half-dozen squall lines each summer, barreling at us from West 
Virginia — and then, we had the June 29, 2012, derecho and all its unforgettable mayhem. Each of those big windstorms were common seasonal weather events pumped up to a higher level by atmospheric steroids. Thursday night, we were back to the garden variety summer squall line. It looked pretty fearsome on radar coming through West Virginia, and there were a small cluster of wind damage reports that way (and quite a few power outages). But as it came into our part of Virginia, it pushed out a shelf cloud (that dark boiling mass that spread out overhead as the wind picked up) that was actually far more picturesque than we saw on June 29, some breezes gusting to about 40 mph (half that of the derecho), some lightning bolts and a little rain. The instability, lift and upper-level wind flow were just not nearly as great today as they were on June 29, and so we got something rather ordinary that resulted in lots of extraordinary photographs. I shared many of these on Twitter tonight as they came in. Matt Wray of Franklin County e-mailed me this panoramic photo of the shelf cloud, which was shot about the same time as this Doppler radar image from the National Weather Service detected the gust front (circled) moving ahead of the actual storm cells in the squall line. And here is a shot of it I took from the roof garden of The Roanoke Times building as the line becomes visible above the mountains northwest of Roanoke.
The factors that produced Thursday’s storms (there were hit-and-miss storms earlier in the afternoon, too) are still present for Friday. In fact, Friday appears likely to be the peak day for this period of storminess (which probably lingers into Saturday), as a cold front to the northwest begins to push a little more into the hot, juicy air mass around us. The Storm Prediction Center, as of Thursday evening, had all of Virginia in a slight risk of severe storms, with damaging winds as the primary threat. Daytime heating — most highs in the 80s, with some in the low 90s — will help get a lot of storms going in the favorable atmospheric environment as the day progresses. Upper-level winds may be a little stronger on Friday, so a few storms may organize into clusters that could produce some severe winds — probably not a large-scale derecho, but some gusty storms. Heavy rain will also be a threat in the strongest storms — the HPC rainfall map favors locations north of us, and as I’ve said before, it’s a little too smoothed out and idealized in its rainfall depiction, as heavier rain will be spotty and some spots may get missed again. It’s a common summer pattern, after all.
July 20, 2012 - 12:12 AM
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Kevin, what effect will the cloud cover today (assuming it stays all day) have on the storms this afternoon/evening?
The less warmth we have today the less instability there will be and the less severe weather risk there will be. The lift of the cold front combined with the warm/sicky air mass will produce showers and storms (and is currently), but the chances of stronger storms will weaken the cooler we stay today.
The Storm Prediction Center has already shifted the slight risk severe zone east of the Blue Ridge partly for this reason.
We got just shy of a half-inch yesterday…I finished mowing the yard and weedeating just a couple minutes before the rains arrived. For a brief time, it rained so hard even the frogs who live in our pond went for cover…
When I awoke this morning to the thick clouds, I figured that would cut back the risk for severe weather. We could still use more rain, but I could go for more of a slow soaking rain…rather than a gullywasher.
One of my company’s employees at our Baltimore office took photos and video last night of the storms that hit there, they got some notable street flooding out of it.
We’re currently sitting at 77.8 in Goodview. We also only received .12 inches from last night’s line. Heading to Snowshoe tomorrow to play the Raven. Should be some soft greens (at least according to radar the last few days), now all I have to do is hit them
Yes, I’m referring to Roanoke Country Club Doug.
And that radar was a big fat liar last night!!! Looked as if the rain was directly above us and I saw the cool shelf cloud but NO RAIN! Not even a drop! Now, Kevin, I know you said it would be spotty for some but I haven’t gotten rain here since Saturday and that was from a small storm cell. I never fare well from these squall lines coming from WV. I’m a bit disappointed I got no rain!
Doug, I should be Mayor of Brownsville…aside from rain on Saturday which was minimal, I have been without rain for the majority of the summer! I will request a ballot.
Kevin: <<>>
Thanks. Yes, Bleak, VERY ! ! Is there an El Nino like explanation for this historic drought?? Could this go on for 2-3 yrs?
Back-to-back La Nina years play some role in the drought, Peppers Ferry. If it’s like the drought periods of the 1930s and 1950s, it could go on longer than 3 years. It’s really already the second year of extreme drought in much of the Southern Plains.
By the way … I had .25 in my gauge total from two different storms (an afternoon pop-up storm and the squall line) a few miles south of Roanoke. The pattern for my location this summer is to sometimes get the periphery of a shower or storm but never get in the core downpours.
NWS dropped our expected high from 91 to 88…still sitting below 80 right now in Goodview. I’m sure in this weather it wouldn’t take much sun to move the temps…but right now it’s fairly steady.
There is a line of storms up in Ohio and Kentucky sliding southeast, pretty slowly. And we’re starting to see some breaks in clouds that could heat things up a bit. Wonder if we’re in for a repeat of Thursday evening’s squall line.
Kevin, I think I’ve heard that while the 30′s was s dry decade that it could have been much worse if the drought years were back to back or worse. I think I read that there were not back to back years of drought. Can you confirm or refute?
Drought record-keeping is much more precise now than it was then — there was no Drought Monitor in the 1930s or even the 1950s. The Dust Bowl in the High Plains region is often referred to as the 1930-36 period. Not sure about the year to year distinctions, will see what I can find.
Rick: Below is linked a National Climatic Data Center summary of U.S. Drought. This sentence seems to confirm what you were saying about multiple waves of drought, and what I was saying about it being considered continuous in the High Plains (though even longer than the 193-36 period.)
“The drought came in three waves, 1934, 1936, and 1939-40, but some regions of the High Plains experienced drought conditions for as many as eight years.”
http://www.ncdc.noaa.gov/paleo/drought/drght_history.html
Kevin and everyone, I once saw a documentary on tv (Nat Geo Channel? History Channel?) a few years ago that showed film of what Oklahoma looked like during the mid- and late-1930s. Incredible dust storms and no grasses, bare trees. Just an amazing wasteland. The Dust Bowl was a primary cause of the great migration of folks from Oklahoma (called “Okies”) to California. And the Depression was still going on then, too.
For you younger folks, you may have been taught that the Depression ended about 1936. Basically not true. Things started to get better about 1936, but then economic recovery waned in 1938-39, also. My father, older brother, and several uncles all maintained that what really got the US economy rolling again was WW2. That basically the Depression lasted throughout the decade of the 1930s, although not nearly as bad for the last 4 years of the 30s.
103F Dallas as I type this,,,
a tease outflow from OK might give us a
puff of cooler air this evening//but doubtful…
Quite envious of the cloud covered low mid 80s
you guys have.
Lookin very “Augusty” down here.
The ground and sky are very tired.
Nothing here just east of Blacksburg last night. Nothing! I can’t remember the last time of so many 50-75% chance of rain and nada happens.
I think we’re in that cycling summer dry pattern where the models forget that the air/ground west of us are devoid of moisture.
Nada is going to happen for most in SW Va tonight, too. The line at the Ohio River is not looking very healthy.
I had a strong premonition throughout this morning when the sun NEVER came out (while I was delivering mail) that most places in the Roanoke valley would not be getting any measurable rain today and this evening. Because I was on a riding route, I was actually rooting for the sun to come out and increase the instability aloft, and goodness sakes there was certainly a moist airmass around (dew points in the mid-60s at least), but it never happened.
Starting to see some pop-up storms in Giles, Floyd and Grayson/Carroll counties. Small but heavy. Some get a downpour, most don’t with these, as they move ENE.
Kevin/Rick, I have read but never saw a map of a severe drought in the 1860s. Have you? A map or detailed description? What I read mentioned S. Cal. and Virginia ?
Here you go, Peppers Ferry — some maps to go with narrative about droughts in the 19th century.
http://www.ldeo.columbia.edu/res/div/ocp/drought/nineteenth.shtml
I think every day this week, the HPC map showed I would get 1-2.5 inches of rain in the next 5 day. Well, so far that has resulted in 0.10″.
Thanks Kevin for the drought information.
I wasn’t a big believer in the HPC numbers — their maps don’t do well in summer scattered patterns, never have — but thought this would pan out more than it did. Maybe half an inch over most of the area with a few heavier stripes.
Drought begets more drought until it is dealt with head-on by major pattern changes. Until we get large-scale storm systems to soak large regions, all we’re going to have are these hit-and-miss pop-up storms and clusters. A few spots will get flooding rains — Petersburg reporting that tonight. Most will get much less or nothing.
I think once El Nino gets going, which may take a few months to influence rainfall patterns, big chunks of the USA will get a fairly quick solution to their lack of rain. Including us. But I am talking at least October, more likely November. And I don’t have the Midwest in mind when I mentioned “big chunks.”
Speaking of El Nino, the latest “ENSO Prediction Plume” has been issued by the IRI. Only about 4 models show this El Nino getting really strong (at/over +1.5 degrees for even one month), and there is general consensus that this El Nino will not last for many months, either. I think nearly all of them show the temps falling gradually starting in the “DJF” timeframe, and definitely by the JFM measurement. So we better get a somewhat wet/moist/snowy winter, because by spring El Nino will probably be back to neutral conditions.
Heavy rain in Galax from earlier storm caused some flooding problems. A couple of streets were closed for a while. Taylorwood’s PWS reporting 2.46″ of rain.
Saw that storm on radar, Johnny.
Below are estimated rain totals from Doppler radar. The northernmost green dot in the circle is the Galax storm Johnny refers to. Very localized.
http://blogs.roanoke.com/weatherjournal/files/2012/07/raintotalradar1040pm0720b.png
I wish a localized storm would come dump on my neighborhood, even to the tune of an inch. Even the new Roanoke Valley Mayor of Brownsville — Leo Lady — would like that, too, I bet. How much rainfall did you get yesterday, LL?
Not much rain here today at the Chapel. Some light, steady rain this am and another light shower this afternoon. Strong storms with heavy rain are now hitting lower Washington Co into Kingsport, Tn and a line toward Knoxville. Lower Washington Co, VA and Sullivan Co, Tn have had over 8″ of rain this month. I estimate our numbers between 3-4 “. Ms. Eva in Mendota is getting rain tonight. Dog days are here for now.
Yep crazy storm here in Galax this evening. The BBQ festival is going on and close to 3″ of rain was reported in several areas in town. A lower lying area was flooded for a time as the run-off overwhelmed the drainage system. My wife was serving beers downtown and said it was one of the strongest downpours she had seen. Less than 4 miles away,I got nothing at home…
Other John, how did your golf outing go today? Was the weather an issue?
Oh yeah, forgot to mention that I GOT NO RAIN TODAY! By now though, I’m used to this…I’m probably more likely to get rain from a small cell when it is least likely…infact, that’s what happened 1-2 weeks ago. Maybe it’ll happen again!